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Tyagi S, Higerd-Rusli GP, Akin EJ, Baker CA, Liu S, Dib-Hajj FB, Waxman SG, Dib-Hajj SD. Real-time imaging of axonal membrane protein life cycles. Nat Protoc 2024:10.1038/s41596-024-00997-x. [PMID: 38831222 DOI: 10.1038/s41596-024-00997-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 02/12/2024] [Indexed: 06/05/2024]
Abstract
The construction of neuronal membranes is a dynamic process involving the biogenesis, vesicular packaging, transport, insertion and recycling of membrane proteins. Optical imaging is well suited for the study of protein spatial organization and transport. However, various shortcomings of existing imaging techniques have prevented the study of specific types of proteins and cellular processes. Here we describe strategies for protein tagging and labeling, cell culture and microscopy that enable the real-time imaging of axonal membrane protein trafficking and subcellular distribution as they progress through some stages of their life cycle. First, we describe a process for engineering membrane proteins with extracellular self-labeling tags (either HaloTag or SNAPTag), which can be labeled with fluorescent ligands of various colors and cell permeability, providing flexibility for investigating the trafficking and spatiotemporal regulation of multiple membrane proteins in neuronal compartments. Next, we detail the dissection, transfection and culture of dorsal root ganglion sensory neurons in microfluidic chambers, which physically compartmentalizes cell bodies and distal axons. Finally, we describe four labeling and imaging procedures that utilize these enzymatically tagged proteins, flexible fluorescent labels and compartmentalized neuronal cultures to study axonal membrane protein anterograde and retrograde transport, the cotransport of multiple proteins, protein subcellular localization, exocytosis and endocytosis. Additionally, we generated open-source software for analyzing the imaging data in a high throughput manner. The experimental and analysis workflows provide an approach for studying the dynamics of neuronal membrane protein homeostasis, addressing longstanding challenges in this area. The protocol requires 5-7 days and expertise in cell culture and microscopy.
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Affiliation(s)
- Sidharth Tyagi
- Medical Scientist Training Program, Yale School of Medicine, New Haven, CT, USA
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Grant P Higerd-Rusli
- Medical Scientist Training Program, Yale School of Medicine, New Haven, CT, USA
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Elizabeth J Akin
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Christopher A Baker
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Shujun Liu
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Fadia B Dib-Hajj
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Stephen G Waxman
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA.
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA.
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA.
| | - Sulayman D Dib-Hajj
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA.
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA.
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA.
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2
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Tang Y, Wu X, Li J, Li Y, Xu X, Li G, Zhang P, Qin C, Wu LJ, Tang Z, Tian DS. The Emerging Role of Microglial Hv1 as a Target for Immunomodulation in Myelin Repair. Aging Dis 2024; 15:1176-1203. [PMID: 38029392 PMCID: PMC11081154 DOI: 10.14336/ad.2023.1107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 11/07/2023] [Indexed: 12/01/2023] Open
Abstract
In the central nervous system (CNS), the myelin sheath ensures efficient interconnection between neurons and contributes to the regulation of the proper function of neuronal networks. The maintenance of myelin and the well-organized subtle process of myelin plasticity requires cooperation among myelin-forming cells, glial cells, and neural networks. The process of cooperation is fragile, and the balance is highly susceptible to disruption by microenvironment influences. Reactive microglia play a critical and complicated role in the demyelination and remyelination process. Recent studies have shown that the voltage-gated proton channel Hv1 is selectively expressed in microglia in CNS, which regulates intracellular pH and is involved in the production of reactive oxygen species, underlying multifaceted roles in maintaining microglia function. This paper begins by examining the molecular mechanisms of demyelination and emphasizes the crucial role of the microenvironment in demyelination. It focuses specifically on the role of Hv1 in myelin repair and its therapeutic potential in CNS demyelinating diseases.
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Affiliation(s)
- Yingxin Tang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Xuan Wu
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Jiarui Li
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Yuanwei Li
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Xiaoxiao Xu
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Gaigai Li
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Ping Zhang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Chuan Qin
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Long-Jun Wu
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA
| | - Zhouping Tang
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Dai-Shi Tian
- Department of Neurology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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3
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Lysko DE, Talbot WS. Unmyelinated sensory neurons use Neuregulin signals to promote myelination of interneurons in the CNS. Cell Rep 2022; 41:111669. [PMID: 36384112 PMCID: PMC9719401 DOI: 10.1016/j.celrep.2022.111669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 09/06/2022] [Accepted: 10/25/2022] [Indexed: 11/17/2022] Open
Abstract
The signaling mechanisms neurons use to modulate myelination of circuits in the central nervous system (CNS) are only partly understood. Through analysis of isoform-specific neuregulin1 (nrg1) mutants in zebrafish, we demonstrate that nrg1 type II is an important regulator of myelination of two classes of spinal cord interneurons. Surprisingly, nrg1 type II expression is prominent in unmyelinated Rohon-Beard sensory neurons, whereas myelination of neighboring interneurons is reduced in nrg1 type II mutants. Cell-type-specific loss-of-function studies indicate that nrg1 type II is required in Rohon-Beard neurons to signal to other neurons, not oligodendrocytes, to modulate spinal cord myelination. Together, our data support a model in which unmyelinated neurons express Nrg1 type II proteins to regulate myelination of neighboring neurons, a mode of action that may coordinate the functions of unmyelinated and myelinated neurons in the CNS.
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Affiliation(s)
- Daniel E Lysko
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | - William S Talbot
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA.
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4
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Deck M, Van Hameren G, Campbell G, Bernard-Marissal N, Devaux J, Berthelot J, Lattard A, Médard JJ, Gautier B, Guelfi S, Abbou S, Quintana P, Chao de la Barca JM, Reynier P, Lenaers G, Chrast R, Tricaud N. Physiology of PNS axons relies on glycolytic metabolism in myelinating Schwann cells. PLoS One 2022; 17:e0272097. [PMID: 36194565 PMCID: PMC9531822 DOI: 10.1371/journal.pone.0272097] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 07/12/2022] [Indexed: 11/18/2022] Open
Abstract
While lactate shuttle theory states that glial cells metabolize glucose into lactate to shuttle it to neurons, how glial cells support axonal metabolism and function remains unclear. Lactate production is a common occurrence following anaerobic glycolysis in muscles. However, several other cell types, including some stem cells, activated macrophages and tumor cells, can produce lactate in presence of oxygen and cellular respiration, using Pyruvate Kinase 2 (PKM2) to divert pyruvate to lactate dehydrogenase. We show here that PKM2 is also upregulated in myelinating Schwann cells (mSC) of mature mouse sciatic nerve versus postnatal immature nerve. Deletion of this isoform in PLP-expressing cells in mice leads to a deficit of lactate in mSC and in peripheral nerves. While the structure of myelin sheath was preserved, mutant mice developed a peripheral neuropathy. Peripheral nerve axons of mutant mice failed to maintain lactate homeostasis upon activity, resulting in an impaired production of mitochondrial ATP. Action potential propagation was not altered but axonal mitochondria transport was slowed down, muscle axon terminals retracted and motor neurons displayed cellular stress. Additional reduction of lactate availability through dichloroacetate treatment, which diverts pyruvate to mitochondrial oxidative phosphorylation, further aggravated motor dysfunction in mutant mice. Thus, lactate production through PKM2 enzyme and aerobic glycolysis is essential in mSC for the long-term maintenance of peripheral nerve axon physiology and function.
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Affiliation(s)
- Marie Deck
- INM, INSERM, Université de Montpellier, Montpellier, France
- * E-mail: (NT); (MD)
| | | | | | | | - Jérôme Devaux
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Jade Berthelot
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Alise Lattard
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Jean-Jacques Médard
- Departments of Clinical Neuroscience and Neuroscience, Karolinska Intitutet, Stockholm, Sweden
| | - Benoît Gautier
- INM, INSERM, Université de Montpellier, Montpellier, France
| | - Sophie Guelfi
- INM, INSERM, Université de Montpellier, Montpellier, France
| | | | | | - Juan Manuel Chao de la Barca
- Département de Biochimie et Génétique, Centre Hospitalier Universitaire, Angers, France
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Pascal Reynier
- Département de Biochimie et Génétique, Centre Hospitalier Universitaire, Angers, France
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Guy Lenaers
- Equipe Mitolab, MITOVASC, CNRS 6015, INSERM U1083, Université d’Angers, Angers, France
| | - Roman Chrast
- Departments of Clinical Neuroscience and Neuroscience, Karolinska Intitutet, Stockholm, Sweden
| | - Nicolas Tricaud
- I-Stem, UEVE/UPS U861, INSERM, AFM, Corbeil-Essonnes, France
- * E-mail: (NT); (MD)
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5
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Vagionitis S, Auer F, Xiao Y, Almeida RG, Lyons DA, Czopka T. Clusters of neuronal neurofascin prefigure the position of a subset of nodes of Ranvier along individual central nervous system axons in vivo. Cell Rep 2022; 38:110366. [PMID: 35172135 PMCID: PMC8864464 DOI: 10.1016/j.celrep.2022.110366] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 07/08/2021] [Accepted: 01/20/2022] [Indexed: 12/23/2022] Open
Abstract
The spacing of nodes of Ranvier crucially affects conduction properties along myelinated axons. It is assumed that node position is primarily driven by growing myelin sheaths. Here, we reveal an additional mechanism of node positioning that is driven by the axon. Through longitudinal live imaging of node formation dynamics in the zebrafish central nervous system, we show that stable clusters of the cell adhesion molecule neurofascin a can accumulate at specific sites along axons prior to myelination. While some of these clusters are pushed into future node position by extending myelin sheaths, others are not and thus prefigure the position of where a mature node forms. Animals that lack full-length neurofascin a show increased internodal distances and less regular nodal spacing along single axons. Together, our data reveal the existence of an axonal mechanism to position nodes of Ranvier that does not depend on regulation by myelin sheath growth. Stable clusters of neuronal neurofascin can form along axons prior to myelination Some clusters are pushed in place by developing myelin sheaths Other clusters restrict sheath growth and thus prefigure node position Animals lacking axonal neurofascin have longer and less regular internodal spacing
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Affiliation(s)
- Stavros Vagionitis
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany
| | - Franziska Auer
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany
| | - Yan Xiao
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany
| | - Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, EH16 4SB Edinburgh, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, EH16 4SB Edinburgh, UK
| | - Tim Czopka
- Institute of Neuronal Cell Biology, Technical University of Munich, 80802 Munich, Germany; Munich Cluster of Systems Neurology (SyNergy), 81377 Munich, Germany; Centre for Clinical Brain Sciences, University of Edinburgh, Chancellor's Building, 49 Little France Crescent, EH16 4SB Edinburgh, UK.
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6
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Swire M, Ffrench-Constant C. Staining and Quantitative Analysis of Myelinating Oligodendrocytes in the Mouse Grey Matter. Bio Protoc 2020; 10:e3792. [PMID: 33659446 DOI: 10.21769/bioprotoc.3792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 08/18/2020] [Accepted: 09/21/2020] [Indexed: 11/02/2022] Open
Abstract
Oligodendrocytes generate distinct patterns of myelination throughout the CNS. Variations in myelination along axons may enable neurons to fine-tune conduction velocities and alter signal synchronisation. Here we outline a staining protocol permitting the assessment of the number and length of myelin sheaths formed by oligodendrocyte in the mouse grey matter. This protocol enables the investigation of myelination without the need for reporter mice or technically challenging protocols, aiding the investigation of factors influencing myelin production in the brain.
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Affiliation(s)
- Matthew Swire
- Wolfson Institute for Biomedical Research, University College London, London, United Kingdom
| | - Charles Ffrench-Constant
- MRC Centre for Regenerative Medicine, MS Society Edinburgh Centre, University of Edinburgh, Edinburgh, United Kingdom
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7
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Bonetto G, Kamen Y, Evans KA, Káradóttir RT. Unraveling Myelin Plasticity. Front Cell Neurosci 2020; 14:156. [PMID: 32595455 PMCID: PMC7301701 DOI: 10.3389/fncel.2020.00156] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 05/11/2020] [Indexed: 12/24/2022] Open
Abstract
Plasticity in the central nervous system (CNS) allows for responses to changing environmental signals. While the majority of studies on brain plasticity focus on neuronal synapses, myelin plasticity has now begun to emerge as a potential modulator of neuronal networks. Oligodendrocytes (OLs) produce myelin, which provides fast signal transmission, allows for synchronization of neuronal inputs, and helps to maintain neuronal function. Thus, myelination is also thought to be involved in learning. OLs differentiate from oligodendrocyte precursor cells (OPCs), which are distributed throughout the adult brain, and myelination continues into late adulthood. This process is orchestrated by numerous cellular and molecular signals, such as axonal diameter, growth factors, extracellular signaling molecules, and neuronal activity. However, the relative importance of, and cooperation between, these signaling pathways is currently unknown. In this review, we focus on the current knowledge about myelin plasticity in the CNS. We discuss new insights into the link between this type of plasticity, learning and behavior, as well as mechanistic aspects of myelin formation that may underlie myelin plasticity, highlighting OPC diversity in the CNS.
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Affiliation(s)
- Giulia Bonetto
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Yasmine Kamen
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Kimberley Anne Evans
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Ragnhildur Thóra Káradóttir
- Wellcome - Medical Research Council Cambridge Stem Cell Institute and Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.,Department of Physiology, Biomedical Centre, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
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8
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Chapman TW, Hill RA. Myelin plasticity in adulthood and aging. Neurosci Lett 2019; 715:134645. [PMID: 31765728 DOI: 10.1016/j.neulet.2019.134645] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 11/06/2019] [Accepted: 11/21/2019] [Indexed: 12/31/2022]
Abstract
The central nervous system maintains the potential for molecular and cellular plasticity throughout life. This flexibility underlies fundamental features of neural circuitry including the brain's ability to sense, store, and properly adapt to everchanging external stimuli on time scales from seconds to years. Evidence for most forms of plasticity are centered around changes in neuronal structure and synaptic strength, however recent data suggests that myelinating oligodendrocytes exhibit certain forms of plasticity in the adult. This plasticity ranges from the generation of entirely new myelinating cells to more subtle changes in myelin sheath length, thickness, and distribution along axons. The extent to which these changes dynamically modify axonal function and neural circuitry and whether they are directly related to mechanisms of learning and memory remains an open question. Here we describe different forms of myelin plasticity, highlight some recent evidence for changes in myelination throughout life, and discuss how defects in these forms of plasticity could be associated with cognitive decline in aging.
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Affiliation(s)
- Timothy W Chapman
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Robert A Hill
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA.
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9
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Abstract
The study of brain plasticity has tended to focus on the synapse, where well-described activity-dependent mechanisms are known to play a key role in learning and memory. However, it is becoming increasingly clear that plasticity occurs beyond the synapse. This review focuses on the emerging concept of white matter plasticity. For example, there is growing evidence, both from animal studies and from human neuroimaging, that activity-dependent regulation of myelin may play a role in learning. This previously overlooked phenomenon may provide a complementary but powerful route through which experience shapes the brain.
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10
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Bar E, Barak B. Microglia roles in synaptic plasticity and myelination in homeostatic conditions and neurodevelopmental disorders. Glia 2019; 67:2125-2141. [DOI: 10.1002/glia.23637] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 04/15/2019] [Accepted: 04/16/2019] [Indexed: 12/28/2022]
Affiliation(s)
- Ela Bar
- The School of Psychological Sciences, Faculty of Social Sciences, and The Sagol School of NeuroscienceTel Aviv University Tel Aviv Israel
- The School of Neurobiology, Biochemistry & Biophysics, Faculty of Life SciencesTel Aviv University Tel Aviv Israel
| | - Boaz Barak
- The School of Psychological Sciences, Faculty of Social Sciences, and The Sagol School of NeuroscienceTel Aviv University Tel Aviv Israel
- The Sagol School of NeuroscienceTel Aviv University Tel Aviv Israel
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11
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Hill RA, Grutzendler J. Uncovering the biology of myelin with optical imaging of the live brain. Glia 2019; 67:2008-2019. [PMID: 31033062 DOI: 10.1002/glia.23635] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 03/26/2019] [Accepted: 04/11/2019] [Indexed: 12/31/2022]
Abstract
Myelin has traditionally been considered a static structure that is produced and assembled during early developmental stages. While this characterization is accurate in some contexts, recent studies have revealed that oligodendrocyte generation and patterns of myelination are dynamic and potentially modifiable throughout life. Unique structural and biochemical properties of the myelin sheath provide opportunities for the development and implementation of multimodal label-free and fluorescence optical imaging approaches. When combined with genetically encoded fluorescent tags targeted to distinct cells and subcellular structures, these techniques offer a powerful methodological toolbox for uncovering mechanisms of myelin generation and plasticity in the live brain. Here, we discuss recent advances in these approaches that have allowed the discovery of several forms of myelin plasticity in developing and adult nervous systems. Using these techniques, long-standing questions related to myelin generation, remodeling, and degeneration can now be addressed.
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Affiliation(s)
- Robert A Hill
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire
| | - Jaime Grutzendler
- Departments of Neurology and Neuroscience, Yale School of Medicine, New Haven, Connecticut
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12
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Almeida RG. The Rules of Attraction in Central Nervous System Myelination. Front Cell Neurosci 2018; 12:367. [PMID: 30374292 PMCID: PMC6196289 DOI: 10.3389/fncel.2018.00367] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 09/27/2018] [Indexed: 12/12/2022] Open
Abstract
The wrapping of myelin around axons is crucial for the development and function of the central nervous system (CNS) of vertebrates, greatly regulating the conduction of action potentials. Oligodendrocytes, the myelinating glia of the CNS, have an intrinsic tendency to wrap myelin around any permissive structure in vitro, but in vivo, myelin is targeted with remarkable specificity only to certain axons. Despite the importance of myelination, the mechanisms by which oligodendrocytes navigate a complex milieu that includes many types of cells and their cellular projections and select only certain axons for myelination remains incompletely understood. In this Mini-review, I highlight recent studies that shed light on the molecular and cellular rules governing CNS myelin targeting.
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Affiliation(s)
- Rafael Góis Almeida
- Centre for Discovery Brain Sciences, The University of Edinburgh, Edinburgh, United Kingdom
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13
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R-Ras1 and R-Ras2 Are Essential for Oligodendrocyte Differentiation and Survival for Correct Myelination in the Central Nervous System. J Neurosci 2018; 38:5096-5110. [PMID: 29720552 DOI: 10.1523/jneurosci.3364-17.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/14/2018] [Accepted: 04/10/2018] [Indexed: 12/21/2022] Open
Abstract
Rapid and effective neural transmission of information requires correct axonal myelination. Modifications in myelination alter axonal capacity to transmit electric impulses and enable pathological conditions. In the CNS, oligodendrocytes (OLs) myelinate axons, a complex process involving various cellular interactions. However, we know little about the mechanisms that orchestrate correct myelination. Here, we demonstrate that OLs express R-Ras1 and R-Ras2. Using female and male mutant mice to delete these proteins, we found that activation of the PI3K/Akt and Erk1/2-MAPK pathways was weaker in mice lacking one or both of these GTPases, suggesting that both proteins coordinate the activity of these two pathways. Loss of R-Ras1 and/or R-Ras2 diminishes the number of OLs in major myelinated CNS tracts and increases the proportion of immature OLs. In R-Ras1-/- and R-Ras2-/--null mice, OLs show aberrant morphologies and fail to differentiate correctly into myelin-forming phenotypes. The smaller OL population and abnormal OL maturation induce severe hypomyelination, with shorter nodes of Ranvier in R-Ras1-/- and/or R-Ras2-/- mice. These defects explain the slower conduction velocity of myelinated axons that we observed in the absence of R-Ras1 and R-Ras2. Together, these results suggest that R-Ras1 and R-Ras2 are upstream elements that regulate the survival and differentiation of progenitors into OLs through the PI3K/Akt and Erk1/2-MAPK pathways for proper myelination.SIGNIFICANCE STATEMENT In this study, we show that R-Ras1 and R-Ras2 play essential roles in regulating myelination in vivo and control fundamental aspects of oligodendrocyte (OL) survival and differentiation through synergistic activation of PI3K/Akt and Erk1/2-MAPK signaling. Mice lacking R-Ras1 and/or R-Ras2 show a diminished OL population with a higher proportion of immature OLs, explaining the observed hypomyelination in main CNS tracts. In vivo electrophysiology recordings demonstrate a slower conduction velocity of nerve impulses in the absence of R-Ras1 and R-Ras2. Therefore, R-Ras1 and R-Ras2 are essential for proper axonal myelination and accurate neural transmission.
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14
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Lifelong cortical myelin plasticity and age-related degeneration in the live mammalian brain. Nat Neurosci 2018; 21:683-695. [PMID: 29556031 PMCID: PMC5920745 DOI: 10.1038/s41593-018-0120-6] [Citation(s) in RCA: 263] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 02/05/2018] [Indexed: 01/30/2023]
Abstract
Axonal myelin increases neural processing speed and efficiency. It is unknown whether patterns of myelin distribution are fixed or whether myelinating oligodendrocytes are continually generated in adulthood and maintain the capacity for structural remodeling. Using high-resolution, intravital label-free and fluorescence optical imaging in mouse cortex, we demonstrate lifelong oligodendrocyte generation occurring in parallel with structural plasticity of individual myelin internodes. Continuous internode formation occurred on both partially myelinated and unmyelinated axons, and the total myelin coverage along individual axons progressed up to two years of age. After peak myelination, gradual oligodendrocyte death and myelin degeneration in aging were associated with pronounced internode loss and myelin debris accumulation within microglia. Thus, cortical myelin remodeling is protracted throughout life, potentially playing critical roles in neuronal network homeostasis. The gradual loss of internodes and myelin degeneration in aging could contribute significantly to brain pathogenesis.
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15
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Tricaud N. Myelinating Schwann Cell Polarity and Mechanically-Driven Myelin Sheath Elongation. Front Cell Neurosci 2018; 11:414. [PMID: 29354031 PMCID: PMC5760505 DOI: 10.3389/fncel.2017.00414] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/11/2017] [Indexed: 11/13/2022] Open
Abstract
Myelin sheath geometry, encompassing myelin sheath thickness relative to internodal length, is critical to optimize nerve conduction velocity and these parameters are carefully adjusted by the myelinating cells in mammals. In the central nervous system these adjustments could regulate neuronal activities while in the peripheral nervous system they lead to the optimization and the reliability of the nerve conduction velocity. However, the physiological and cellular mechanisms that underlie myelin sheath geometry regulation are not yet fully elucidated. In peripheral nerves the myelinating Schwann cell uses several molecular mechanisms to reach and maintain the correct myelin sheath geometry, such that myelin sheath thickness and internodal length are regulated independently. One of these mechanisms is the epithelial-like cell polarization process that occurs during the early phases of the myelin biogenesis. Epithelial cell polarization factors are known to control cell size and morphology in invertebrates and mammals making these processes critical in the organogenesis. Correlative data indicate that internodal length is regulated by postnatal body growth that elongates peripheral nerves in mammals. In addition, the mechanical stretching of peripheral nerves in adult animals shows that myelin sheath length can be increased by mechanical cues. Recent results describe the important role of YAP/TAZ co-transcription factors during Schwann cell myelination and their functions have linked to the mechanotransduction through the HIPPO pathway and the epithelial polarity factor Crb3. In this review the molecular mechanisms that govern mechanically-driven myelin sheath elongation and how a Schwann cell can modulate internodal myelin sheath length, independent of internodal thickness, will be discussed regarding these recent data. In addition, the potential relevance of these mechanosensitive mechanisms in peripheral pathologies will be highlighted.
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Affiliation(s)
- Nicolas Tricaud
- Institut National de la Santé et de la Recherche Médicale, Institut des Neurosciences de Montpellier, Université de Montpellier, Montpellier, France
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Saifetiarova J, Liu X, Taylor AM, Li J, Bhat MA. Axonal domain disorganization in Caspr1 and Caspr2 mutant myelinated axons affects neuromuscular junction integrity, leading to muscle atrophy. J Neurosci Res 2017; 95:1373-1390. [PMID: 28370195 DOI: 10.1002/jnr.24052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 02/14/2017] [Accepted: 02/24/2017] [Indexed: 12/19/2022]
Abstract
Bidirectional interactions between neurons and myelinating glial cells result in formation of axonal domains along myelinated fibers. Loss of axonal domains leads to detrimental consequences on nerve structure and function, resulting in reduced conductive properties and the diminished ability to reliably transmit signals to the targets they innervate. Thus, impairment of peripheral myelinated axons that project to the surface of muscle fibers and form neuromuscular junction (NMJ) synapses leads to muscle dysfunction. The goal of our studies was to determine how altered electrophysiological properties due to axonal domain disorganization lead to muscle pathology, which is relevant to a variety of peripheral neuropathies, demyelinating diseases, and neurodegenerative disorders. Using conventional Contactin-Associated Protein 1 (Caspr1) and Caspr2 single or double mutants with disrupted paranodal, juxtaparanodal, or both regions, respectively, in peripheral myelinated axons, we correlated defects in NMJ integrity and muscle pathology. Our data show that loss of axonal domains in Caspr1 and Caspr2 single and double mutants primarily alters distal myelinated fibers together with presynaptic terminals, eventually leading to NMJ denervation and reduction in postsynaptic endplate areas. Moreover, reduction in conductive properties of peripheral myelinated fibers together with NMJ disintegration leads to muscle atrophy in Caspr1 mutants or muscle fiber degeneration accompanied by mitochondrial dysfunction in Caspr1/Caspr2 double mutants. Together, our data indicate that proper organization of axonal domains in myelinated fibers is critical for optimal propagation of electrical signals, NMJ integrity, and muscle health, and provide insights into a wide range of pathologies that result in reduced nerve conduction leading to muscle atrophy. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Julia Saifetiarova
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Xi Liu
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas.,Xiangya School of Medicine, Central South University, Changsha, China
| | - Anna M Taylor
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Jie Li
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Manzoor A Bhat
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, School of Medicine, University of Texas Health Science Center, San Antonio, Texas
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17
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Fontenas L, De Santis F, Di Donato V, Degerny C, Chambraud B, Del Bene F, Tawk M. Neuronal Ndrg4 Is Essential for Nodes of Ranvier Organization in Zebrafish. PLoS Genet 2016; 12:e1006459. [PMID: 27902705 PMCID: PMC5130175 DOI: 10.1371/journal.pgen.1006459] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 11/03/2016] [Indexed: 11/19/2022] Open
Abstract
Axon ensheathment by specialized glial cells is an important process for fast propagation of action potentials. The rapid electrical conduction along myelinated axons is mainly due to its saltatory nature characterized by the accumulation of ion channels at the nodes of Ranvier. However, how these ion channels are transported and anchored along axons is not fully understood. We have identified N-myc downstream-regulated gene 4, ndrg4, as a novel factor that regulates sodium channel clustering in zebrafish. Analysis of chimeric larvae indicates that ndrg4 functions autonomously within neurons for sodium channel clustering at the nodes. Molecular analysis of ndrg4 mutants shows that expression of snap25 and nsf are sharply decreased, revealing a role of ndrg4 in controlling vesicle exocytosis. This uncovers a previously unknown function of ndrg4 in regulating vesicle docking and nodes of Ranvier organization, at least through its ability to finely tune the expression of the t-SNARE/NSF machinery. Myelination is an important process that enables fast propagation of action potential along the axons. Schwann cells (SCs) are the specialized glial cells that ensure the ensheathment of the corresponding axons in the Peripheral Nervous System. In order to do so, SCs and axons need to communicate to organize the myelinating segments and the clustering of sodium channels at the nodes of Ranvier. We have investigated the early events of myelination in the zebrafish embryo. We here identify ndrg4 as a novel neuronal factor essential for sodium channel clustering at the nodes. Immuno-labeling analysis show defective vesicle patterning along the axons of ndrg4 mutants, while timelapse experiments monitoring the presence and the transport of these vesicles reveal a normal behavior. Molecular analysis unravels a novel function of ndrg4 in controlling the expression of the t-SNARE/NSF machinery required for vesicle docking and release. However, inhibiting specifically regulated synaptic vesicle release does not lead to sodium channel clustering defects. We thus propose that ndrg4 can regulate this process, at least partially, through its ability to regulate the expression of key components of the t-SNARE/NSF machinery, responsible for clustering of sodium channels along myelinated axons.
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Affiliation(s)
- Laura Fontenas
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
| | | | | | - Cindy Degerny
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
| | - Béatrice Chambraud
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
| | | | - Marcel Tawk
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
- * E-mail:
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18
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Almeida R, Lyons D. Oligodendrocyte Development in the Absence of Their Target Axons In Vivo. PLoS One 2016; 11:e0164432. [PMID: 27716830 PMCID: PMC5055324 DOI: 10.1371/journal.pone.0164432] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 09/26/2016] [Indexed: 11/19/2022] Open
Abstract
Oligodendrocytes form myelin around axons of the central nervous system, enabling saltatory conduction. Recent work has established that axons can regulate certain aspects of oligodendrocyte development and myelination, yet remarkably oligodendrocytes in culture retain the ability to differentiate in the absence of axons and elaborate myelin sheaths around synthetic axon-like substrates. It remains unclear the extent to which the life-course of oligodendrocytes requires the presence of, or signals derived from axons in vivo. In particular, it is unclear whether the specific axons fated for myelination regulate the oligodendrocyte population in a living organism, and if so, which precise steps of oligodendrocyte-cell lineage progression are regulated by target axons. Here, we use live-imaging of zebrafish larvae carrying transgenic reporters that label oligodendrocyte-lineage cells to investigate which aspects of oligodendrocyte development, from specification to differentiation, are affected when we manipulate the target axonal environment. To drastically reduce the number of axons targeted for myelination, we use a previously identified kinesin-binding protein (kbp) mutant, in which the first myelinated axons in the spinal cord, reticulospinal axons, do not fully grow in length, creating a region in the posterior spinal cord where most initial targets for myelination are absent. We find that a 73% reduction of reticulospinal axon surface in the posterior spinal cord of kbp mutants results in a 27% reduction in the number of oligodendrocytes. By time-lapse analysis of transgenic OPC reporters, we find that the reduction in oligodendrocyte number is explained by a reduction in OPC proliferation and survival. Interestingly, OPC specification and migration are unaltered in the near absence of normal axonal targets. Finally, we find that timely differentiation of OPCs into oligodendrocytes does not depend at all on the presence of target axons. Together, our data illustrate the power of zebrafish for studying the entire life-course of the oligodendrocyte lineage in vivo in an altered axonal environment.
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Affiliation(s)
- Rafael Almeida
- Centre for Neuroregeneration, University of Edinburgh, Edinburgh, United Kingdom
- MS Society Centre for Translational Research, University of Edinburgh, Edinburgh, United Kingdom
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (RA); (DL)
| | - David Lyons
- Centre for Neuroregeneration, University of Edinburgh, Edinburgh, United Kingdom
- MS Society Centre for Translational Research, University of Edinburgh, Edinburgh, United Kingdom
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (RA); (DL)
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19
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Optimal myelin elongation relies on YAP activation by axonal growth and inhibition by Crb3/Hippo pathway. Nat Commun 2016; 7:12186. [PMID: 27435623 PMCID: PMC4961766 DOI: 10.1038/ncomms12186] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 06/09/2016] [Indexed: 01/24/2023] Open
Abstract
Fast nerve conduction relies on successive myelin segments that electrically isolate axons. Segment geometry—diameter and length—is critical for the optimization of nerve conduction and the molecular mechanisms allowing this optimized geometry are partially known. We show here that peripheral myelin elongation is dynamically regulated by stimulation of YAP (Yes-associated protein) transcription cofactor activity during axonal elongation and limited by inhibition of YAP activity via the Hippo pathway. YAP promotes myelin and non-myelin genes transcription while the polarity protein Crb3, localized at the tips of the myelin sheath, activates the Hippo pathway to temper YAP activity, therefore allowing for optimal myelin growth. Dystrophic Dy2j/2j mice mimicking human peripheral neuropathy with reduced internodal lengths have decreased nuclear YAP which, when corrected, leads to longer internodes. These data show a novel mechanism controlling myelin growth and nerve conduction, and provide a molecular ground for disease with short myelin segments. Molecular mechanisms regulating optimal myelin geometry are only partially understood. Here authors show that peripheral myelin growth is orchestrated by the Crb3/Hippo/YAP pathway, and that defects in YAP activation may underlie peripheral neuropathies caused by shorter myelin.
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20
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Abstract
A variety of anatomical features suggest that functional activity in the nervous system can influence the process of myelination, yet direct evidence of this is lacking. Research by Zalc and colleagues shows that myelination of optic nerve is inhibited by a neurotoxin that blocks action potential activity and is stimulated by a toxin that increases impulse activity, suggesting that impulse activity is necessary for initiating myelination during development of the optic nerve. Research by Fields and colleagues, using electrical stimulation of axons, shows that low frequency impulse activity inhibits myelination of dorsal root ganglion neurons, but high frequency impulse activity has no effect. This results from reduced expression of a cell adhesion molecule on the stimulated axons that is critical for inducing myelination. Together these studies support the conclusion that impulse activity can influence the process of myelination, probably through more than one molecular mechanism operating during discrete steps in the myelination process.
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Affiliation(s)
- Bernard Zalc
- Biologie des Interactions Neurones-Glie, Institut National de la Santé et de la Recherche Médicale U-495, Université P. M. Curie, Hôpital de la Salpêtrière, Paris, France (BZ), Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland (RDF)
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21
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Chang KJ, Redmond SA, Chan JR. Remodeling myelination: implications for mechanisms of neural plasticity. Nat Neurosci 2016; 19:190-7. [PMID: 26814588 DOI: 10.1038/nn.4200] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Accepted: 10/12/2015] [Indexed: 02/08/2023]
Abstract
One of the most significant paradigm shifts in membrane remodeling is the emerging view that membrane transformation is not exclusively controlled by cytoskeletal rearrangement, but also by biophysical constraints, adhesive forces, membrane curvature and compaction. One of the most exquisite examples of membrane remodeling is myelination. The advent of myelin was instrumental in advancing the nervous system during vertebrate evolution. With more rapid and efficient communication between neurons, faster and more complex computations could be performed in a given time and space. Our knowledge of how myelin-forming oligodendrocytes select and wrap axons has been limited by insufficient spatial and temporal resolution. By virtue of recent technological advances, progress has clarified longstanding controversies in the field. Here we review insights into myelination, from target selection to axon wrapping and membrane compaction, and discuss how understanding these processes has unexpectedly opened new avenues of insight into myelination-centered mechanisms of neural plasticity.
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Affiliation(s)
- Kae-Jiun Chang
- Department of Neurology, University of California, San Francisco, California, USA
| | - Stephanie A Redmond
- Department of Neurology, University of California, San Francisco, California, USA.,Program in Neuroscience, University of California, San Francisco, California, USA
| | - Jonah R Chan
- Department of Neurology, University of California, San Francisco, California, USA.,Program in Neuroscience, University of California, San Francisco, California, USA
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22
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Murcia-Belmonte V, Esteban PF, Martínez-Hernández J, Gruart A, Luján R, Delgado-García JM, de Castro F. Anosmin-1 over-expression regulates oligodendrocyte precursor cell proliferation, migration and myelin sheath thickness. Brain Struct Funct 2015; 221:1365-85. [PMID: 25662897 DOI: 10.1007/s00429-014-0977-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 12/22/2014] [Indexed: 12/11/2022]
Abstract
During development of the central nervous system, anosmin-1 (A1) works as a chemotropic cue contributing to axonal outgrowth and collateralization, as well as modulating the migration of different cell types, fibroblast growth factor receptor 1 (FGFR1) being the main receptor involved in all these events. To further understand the role of A1 during development, we have analysed the over-expression of human A1 in a transgenic mouse line. Compared with control mice during development and in early adulthood, A1 over-expressing transgenic mice showed an enhanced oligodendrocyte precursor cell (OPC) proliferation and a higher number of OPCs in the subventricular zone and in the corpus callosum (CC). The migratory capacity of OPCs from the transgenic mice is increased in vitro due to a higher basal activation of ERK1/2 mediated through FGFR1 and they also produced more myelin basic protein (MBP). In vivo, the over-expression of A1 resulted in an elevated number of mature oligodendrocytes with higher levels of MBP mRNA and protein, as well as increased levels of activation of the ERK1/2 proteins, while electron microscopy revealed thicker myelin sheaths around the axons of the CC in adulthood. Also in the mature CC, the nodes of Ranvier were significantly longer and the conduction velocity of the nerve impulse in vivo was significantly increased in the CC of A1 over-expressing transgenic mice. Altogether, these data confirmed the involvement of A1 in oligodendrogliogenesis and its relevance for myelination.
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Affiliation(s)
- Verónica Murcia-Belmonte
- Grupo de Neurobiología del Desarrollo-GNDe, Hospital Nacional de Parapléjicos, Finca La Peraleda, s/n, 45071, Toledo, Spain.,Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, Campus San Juan de Alicante, 03550, Alicante, Spain
| | - Pedro F Esteban
- Grupo de Neurobiología del Desarrollo-GNDe, Hospital Nacional de Parapléjicos, Finca La Peraleda, s/n, 45071, Toledo, Spain
| | - José Martínez-Hernández
- Departamento de Ciencias Médicas, CRIB-Facultad de Medicina, Universidad de Castilla-La Mancha, C/Almansa 14, 02006, Albacete, Spain
| | - Agnès Gruart
- División de Neurociencias, Universidad Pablo de Olavide, Ctra. De Utrera, Km.1, 41013, Seville, Spain
| | - Rafael Luján
- Departamento de Ciencias Médicas, CRIB-Facultad de Medicina, Universidad de Castilla-La Mancha, C/Almansa 14, 02006, Albacete, Spain
| | - José María Delgado-García
- División de Neurociencias, Universidad Pablo de Olavide, Ctra. De Utrera, Km.1, 41013, Seville, Spain
| | - Fernando de Castro
- Grupo de Neurobiología del Desarrollo-GNDe, Hospital Nacional de Parapléjicos, Finca La Peraleda, s/n, 45071, Toledo, Spain.
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23
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Sui T, Zhang J, Du S, Su C, Que J, Cao X. Potential risk of mitomycin C at high concentrations on peripheral nerve structure. Neural Regen Res 2014; 9:821-7. [PMID: 25206895 PMCID: PMC4146259 DOI: 10.4103/1673-5374.131598] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2014] [Indexed: 11/04/2022] Open
Abstract
Although the local application of mitomycin C may prevent epidural adhesion after laminectomy, mitomycin C can induce neurotoxicity in optic and acoustic nerves at high concentrations. To determine the safe concentration range for mitomycin C, cotton pads soaked with mitomycin C at different concentrations (0.1, 0.3, 0.5, and 0.7 mg/mL) were immediately applied for 5 minutes to the operation area of rats that had undergone laminectomy at L1. Rat sciatic nerves, instead of dorsal nerves, were used in this study. The results showed that mitomycin C at 0.1-0.5 mg/mL did not damage the structure and function of the sciatic nerve, while at 0.7 mg/mL, mitomycin C significantly reduced the thickness of the sciatic nerve myelin sheath compared with lower concentrations, though no functional change was found. These experimental findings indicate that the local application of mitomycin C at low concentrations is safe to prevent scar adhesion following laminectomy, but that mitomycin C at high concentrations (> 0.7 mg/mL) has potential safety risks to peripheral nerve structures.
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Affiliation(s)
- Tao Sui
- Department of Orthopedics, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Jinhong Zhang
- Department of Orthopedics, the Second Hospital of Nanjing, Affiliated to Southeast University, Nanjing, Jiangsu Province, China
| | - Shihao Du
- Department of Orthopedics, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Changhui Su
- Department of Orthopedics, Affiliated Hospital of Taishan Medical College, Taishan, Shandong Province, China
| | - Jun Que
- Department of Intensive Care Unit, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Xiaojian Cao
- Department of Orthopedics, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China
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24
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Stiefel KM, Torben-Nielsen B, Coggan JS. Proposed evolutionary changes in the role of myelin. Front Neurosci 2013; 7:202. [PMID: 24265603 PMCID: PMC3820973 DOI: 10.3389/fnins.2013.00202] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 10/13/2013] [Indexed: 12/30/2022] Open
Abstract
Myelin is the multi-layered lipid sheet periodically wrapped around neuronal axons. It is most frequently found in vertebrates. Myelin allows for saltatory action potential (AP) conduction along axons. During this form of conduction, the AP travels passively along the myelin-covered part of the axon, and is recharged at the intermittent nodes of Ranvier. Thus, myelin can reduce the energy load needed and/or increase the speed of AP conduction. Myelin first evolved during the Ordovician period. We hypothesize that myelin's first role was mainly energy conservation. During the later "Mesozoic marine revolution," marine ecosystems changed toward an increase in marine predation pressure. We hypothesize that the main purpose of myelin changed from energy conservation to conduction speed increase during this Mesozoic marine revolution. To test this hypothesis, we optimized models of myelinated axons for a combination of AP conduction velocity and energy efficiency. We demonstrate that there is a trade-off between these objectives. We then compared the simulation results to empirical data and conclude that while the data are consistent with the theory, additional measurements are necessary for a complete evaluation of the proposed hypothesis.
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Affiliation(s)
- Klaus M. Stiefel
- The MARCS Institute, Sydney, University of Western SydneyNSW, Australia
| | - Benjamin Torben-Nielsen
- The Blue Brain Project, Ecole Polytechnique Fédérale de LausanneLausanne, Switzerland
- Department of Neurobiology, Hebrew University of Jerusalem, Edmond J. Safra CampusJerusalem, Israel
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25
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Wu B, Guo S, Jiang T, Ren X. In vitroculture and characterization of oligodendrocyte precursor cells derived from neonatal rats. Neurol Res 2013; 33:593-9. [DOI: 10.1179/1743132810y.0000000024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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26
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Seidl AH. Regulation of conduction time along axons. Neuroscience 2013; 276:126-34. [PMID: 23820043 DOI: 10.1016/j.neuroscience.2013.06.047] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/13/2013] [Accepted: 06/17/2013] [Indexed: 11/17/2022]
Abstract
Timely delivery of information is essential for proper functioning of the nervous system. Precise regulation of nerve conduction velocity is needed for correct exertion of motor skills, sensory integration and cognitive functions. In vertebrates, the rapid transmission of signals along nerve fibers is made possible by the myelination of axons and the resulting saltatory conduction in between nodes of Ranvier. Myelin is a specialization of glia cells and is provided by oligodendrocytes in the central nervous system. Myelination not only maximizes conduction velocity, but also provides a means to systematically regulate conduction times in the nervous system. Systematic regulation of conduction velocity along axons, and thus systematic regulation of conduction time in between neural areas, is a common occurrence in the nervous system. To date, little is understood about the mechanism that underlies systematic conduction velocity regulation and conduction time synchrony. Node assembly, internode distance (node spacing) and axon diameter - all parameters determining the speed of signal propagation along axons - are controlled by myelinating glia. Therefore, an interaction between glial cells and neurons has been suggested. This review summarizes examples of neural systems in which conduction velocity is regulated by anatomical variations along axons. While functional implications in these systems are not always clear, recent studies on the auditory system of birds and mammals present examples of conduction velocity regulation in systems with high temporal precision and a defined biological function. Together these findings suggest an active process that shapes the interaction between axons and myelinating glia to control conduction velocity along axons. Future studies involving these systems may provide further insight into how specific conduction times in the brain are established and maintained in development. Throughout the text, conduction velocity is used for the speed of signal propagation, i.e. the speed at which an action potential travels. Conduction time refers to the time it takes for a specific signal to travel from its origin to its target, i.e. neuronal cell body to axonal terminal.
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Affiliation(s)
- A H Seidl
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, WA, USA; Department of Otolaryngology - Head & Neck Surgery, University of Washington, Seattle, WA, USA.
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27
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Park J, Koito H, Li J, Han A. Multi-compartment neuron-glia co-culture platform for localized CNS axon-glia interaction study. LAB ON A CHIP 2012; 12:3296-304. [PMID: 22828584 PMCID: PMC3426455 DOI: 10.1039/c2lc40303j] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Formation of myelin sheaths by oligodendrocytes (OLs) in the central nervous system (CNS) is essential for rapid nerve impulse conduction. Reciprocal signaling between axons and OLs orchestrates myelinogenesis but remains largely elusive. In this study, we present a multi-compartment CNS neuron-glia microfluidic co-culture platform. The platform is capable of conducting parallel localized drug and biomolecule treatments while carrying out multiple co-culture conditions in a single device for studying axon-glia interactions at a higher throughput. The "micro-macro hybrid soft-lithography master fabrication" (MMHSM) technique enables a large number of precisely replicated PDMS devices incorporating both millimeter and micrometer scale structures to be rapidly fabricated without any manual reservoir punching processes. Axons grown from the neuronal somata were physically and fluidically isolated inside the six satellite axon/glia compartments for localized treatments. Astrocytes, when seeded and co-cultured after the establishment of the isolated axons in the satellite axon/glia compartments, were found to physically damage the established axonal layer, as they tend to grow underneath the axons. In contrast, oligodendrocyte progenitor cells (OPCs) could be co-cultured successfully with the isolated axons and differentiated into mature myelin basic protein-expressing OLs with processes aligning to neighboring axons. OPCs inside the six axon/glia compartments were treated with a high concentration of ceramide (150 μM) to confirm the fluidic isolation among the satellite compartments. In addition, isolated axons were treated with varying concentrations of chondroitin sulfate proteoglycan (CSPG, 0-25 μg ml(-1)) within a single device to demonstrate the parallel localized biomolecular treatment capability of the device. These results indicate that the proposed platform can be used as a powerful tool to study CNS axonal biology and axon-glia interactions with the capacity for localized biomolecular treatments.
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Affiliation(s)
- Jaewon Park
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Hisami Koito
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA
| | - Jianrong Li
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA. Fax: 979-847-8981; Tel: 979-862-7155;
| | - Arum Han
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843, USA
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
- Department of Electrical and Computer Engineering & Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA. Fax: 979-845-6259; Tel: 979-845-9686;
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28
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Wu B, Sun L, Li P, Tian M, Luo Y, Ren X. Transplantation of oligodendrocyte precursor cells improves myelination and promotes functional recovery after spinal cord injury. Injury 2012; 43:794-801. [PMID: 22018607 DOI: 10.1016/j.injury.2011.09.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 09/11/2011] [Accepted: 09/12/2011] [Indexed: 02/02/2023]
Abstract
Loss of oligodendrocytes and demyelination further impair neural function after spinal cord injury (SCI). Replacement of lost oligodendrocytes and improvement of myelination have a therapeutic significance in treatment of SCI. Here, we transplanted oligodendrocyte precursor cells (OPCs) to improve myelination in a rat model of contusive SCI. The labelled OPCs were transplanted to injured cord 7 days after injury. As a result, the implanted cells still survived in vivo 8 weeks after transplantation. They proliferated, integrated and differentiated in the injured cord. In the OPCs-treated rats, enhanced myelination in the lesioned area was observed and substantial improvement of motor function and nerve conduction was also recorded. Thus, this study provides strong evidence to support that transplantation of OPCs could improve myelination of injured cord and enhance functional recovery after contusive SCI.
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Affiliation(s)
- Bo Wu
- Department of Orthopedics, 88th Hospital, Tai'an, Shandong, China
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29
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Expression changes of the neuregulin 1 isoforms in neuropathic pain model rats. Neurosci Lett 2012; 508:78-83. [DOI: 10.1016/j.neulet.2011.12.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 12/13/2011] [Accepted: 12/14/2011] [Indexed: 11/21/2022]
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30
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Affiliation(s)
- Dominique Debanne
- INSERM, U641, Marseille, 13344 France
- Université de la Méditerranée, Faculté de Médecine secteur nord, IFR 11, Marseille, 13344 France
| | - Sylvain Rama
- INSERM, U641, Marseille, 13344 France
- Université de la Méditerranée, Faculté de Médecine secteur nord, IFR 11, Marseille, 13344 France
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31
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Pals1 is a major regulator of the epithelial-like polarization and the extension of the myelin sheath in peripheral nerves. J Neurosci 2010; 30:4120-31. [PMID: 20237282 DOI: 10.1523/jneurosci.5185-09.2010] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Diameter, organization, and length of the myelin sheath are important determinants of the nerve conduction velocity, but the basic molecular mechanisms that control these parameters are only partially understood. Cell polarization is an essential feature of differentiated cells, and relies on a set of evolutionarily conserved cell polarity proteins. We investigated the molecular nature of myelin sheath polarization in connection with the functional role of the cell polarity protein pals1 (Protein Associated with Lin Seven 1) during peripheral nerve myelin sheath extension. We found that, in regard to epithelial polarity, the Schwann cell outer abaxonal domain represents a basolateral-like domain, while the inner adaxonal domain and Schmidt-Lanterman incisures form an apical-like domain. Silencing of pals1 in myelinating Schwann cells in vivo resulted in a severe reduction of myelin sheath thickness and length. Except for some infoldings, the structure of compact myelin was not fundamentally affected, but cells produced less myelin turns. In addition, pals1 is required for the normal polarized localization of the vesicular markers sec8 and syntaxin4, and for the distribution of E-cadherin and myelin proteins PMP22 and MAG at the plasma membrane. Our data show that the polarity protein pals1 plays an essential role in the radial and longitudinal extension of the myelin sheath, likely involving a functional role in membrane protein trafficking. We conclude that regulation of epithelial-like polarization is a critical determinant of myelin sheath structure and function.
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32
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Cotter L, Ozçelik M, Jacob C, Pereira JA, Locher V, Baumann R, Relvas JB, Suter U, Tricaud N. Dlg1-PTEN interaction regulates myelin thickness to prevent damaging peripheral nerve overmyelination. Science 2010; 328:1415-8. [PMID: 20448149 DOI: 10.1126/science.1187735] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The thickness of the myelin sheath that insulates axons is fitted for optimal nerve conduction velocity. Here, we show that, in Schwann cells, mammalian disks large homolog 1 (Dlg1) interacts with PTEN (phosphatase and tensin homolog deleted on chromosome 10) to inhibit axonal stimulation of myelination. This mechanism limits myelin sheath thickness and prevents overmyelination in mouse sciatic nerves. Removing this brake results also in myelin outfoldings and demyelination, characteristics of some peripheral neuropathies. Indeed, the Dlg1 brake is no longer functional in a mouse model of Charcot-Marie-Tooth disease. Therefore, negative regulation of myelination appears to be essential for optimization of nerve conduction velocity and myelin maintenance.
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Affiliation(s)
- Laurent Cotter
- Institute of Cell Biology, Department of Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
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33
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Wu B, Ren X. Promoting Axonal Myelination for Improving Neurological Recovery in Spinal Cord Injury. J Neurotrauma 2009; 26:1847-56. [PMID: 19785544 DOI: 10.1089/neu.2008.0551] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- Bo Wu
- Department of Orthopedics, Xinqiao Hospital, The Third Military Medical University, Chongqing, China
- Department of Orthopedics, 88th Hospital, Taian, Shangdong, China
| | - Xianjun Ren
- Department of Orthopedics, Xinqiao Hospital, The Third Military Medical University, Chongqing, China
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34
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Tang J, Tang J, Ling EA, Wu Y, Liang F. Juxtanodin in the rat olfactory epithelium: specific expression in sustentacular cells and preferential subcellular positioning at the apical junctional belt. Neuroscience 2009; 161:249-58. [PMID: 19332107 DOI: 10.1016/j.neuroscience.2009.03.051] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 03/16/2009] [Accepted: 03/16/2009] [Indexed: 10/21/2022]
Abstract
In the CNS, juxtanodin (JN) is an actin-binding oligodendroglial protein that functions to promote differentiation of the host cells during postnatal development. In other tissues, JN expression and function remain unknown. We surveyed rat peripheral nerve, skeletal muscle and various epithelial tissues using immunoblotting and light-microscopic immunohistochemistry, and found prominent JN expression only in the olfactory epithelium (OE). Confocal and immunoelectron microscopy further revealed specific JN expression in the glia-like sustentacular cells and in the ductal cells of Bowman's glands. JN immunoreactivity was especially prominent in sustentacular cell apices extending superficially from the zone of terminal webs and associated adherens junctions, through the zone of tight junctions, to the roots of sustentacular microvilli. Moderate JN was also found in the supranuclear regions of sustentacular cells, whereas distal parts of sustentacular microvilli were devoid of JN. Distribution of JN in the OE differed from that of class III beta-tubulin or nestin, but partially overlapped with a zone of intense F-actin staining near the OE mucous surface. Together these results identify JN as a marker protein for OE sustentacular cells, and support the glia-like nature of OE sustentacular cells. Functionally, JN in the OE might help in the molecular specialization of distinct compartments of olfactory receptor neurons (ORNs), in the interaction of sustentacular cells with ORNs, and/or in maturation/maintenance of sustentacular cells.
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Affiliation(s)
- J Tang
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Block MD10, 4 Medical Drive, Singapore 117597
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35
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Salzer JL, Brophy PJ, Peles E. Molecular domains of myelinated axons in the peripheral nervous system. Glia 2009; 56:1532-1540. [PMID: 18803321 DOI: 10.1002/glia.20750] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Myelinated axons are organized into a series of specialized domains with distinct molecular compositions and functions. These domains, which include the node of Ranvier, the flanking paranodal junctions, the juxtaparanodes, and the internode, form as the result of interactions with myelinating Schwann cells. This domain organization is essential for action potential propagation by saltatory conduction and for the overall function and integrity of the axon.
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Affiliation(s)
- James L Salzer
- Department of Cell Biology and Neurology, and the Smilow Neuroscience Program, NYU School of Medicine, New York, New York 10016, USA.
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36
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Savvaki M, Panagiotaropoulos T, Stamatakis A, Sargiannidou I, Karatzioula P, Watanabe K, Stylianopoulou F, Karagogeos D, Kleopa KA. Impairment of learning and memory in TAG-1 deficient mice associated with shorter CNS internodes and disrupted juxtaparanodes. Mol Cell Neurosci 2008; 39:478-90. [PMID: 18760366 DOI: 10.1016/j.mcn.2008.07.025] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2008] [Revised: 07/29/2008] [Accepted: 07/31/2008] [Indexed: 10/21/2022] Open
Abstract
The cell adhesion molecule TAG-1 is expressed by neurons and glial cells and plays a role in axon outgrowth, migration and fasciculation during development. TAG-1 is also required for the clustering of Kv1.1/1.2 potassium channels and Caspr2 at the juxtaparanodes of myelinated fibers. Behavioral examination of TAG-1 deficient mice (Tag-1(-/-)) showed cognitive impairments in the Morris water maze and novel object recognition tests, reduced spontaneous motor activity, abnormal gait coordination and increased response latency to noxious stimulation. Investigation at the molecular level revealed impaired juxtaparanodal clustering of Caspr2 and Kv1.1/1.2 in the hippocampus, entorhinal cortex, cerebellum and olfactory bulb, with diffusion into the internode. Caspr2 and Kv1.1 levels were reduced in the cerebellum and olfactory bulb. Moreover, Tag-1(-/-) mice had shorter internodes in the cerebral and cerebellar white matter. The detected molecular alterations may account for the behavioural deficits and hyperexcitability in these animals.
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Affiliation(s)
- Maria Savvaki
- Department of Basic Science, University of Crete Medical School, and Institute of Molecular Biology and Biotechnology, Heraklion, Greece
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37
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Bakkum DJ, Chao ZC, Potter SM. Long-term activity-dependent plasticity of action potential propagation delay and amplitude in cortical networks. PLoS One 2008; 3:e2088. [PMID: 18461127 PMCID: PMC2324202 DOI: 10.1371/journal.pone.0002088] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2007] [Accepted: 04/06/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The precise temporal control of neuronal action potentials is essential for regulating many brain functions. From the viewpoint of a neuron, the specific timings of afferent input from the action potentials of its synaptic partners determines whether or not and when that neuron will fire its own action potential. Tuning such input would provide a powerful mechanism to adjust neuron function and in turn, that of the brain. However, axonal plasticity of action potential timing is counter to conventional notions of stable propagation and to the dominant theories of activity-dependent plasticity focusing on synaptic efficacies. METHODOLOGY/PRINCIPAL FINDINGS Here we show the occurrence of activity-dependent plasticity of action potential propagation delays (up to 4 ms or 40% after minutes and 13 ms or 74% after hours) and amplitudes (up to 87%). We used a multi-electrode array to induce, detect, and track changes in propagation in multiple neurons while they adapted to different patterned stimuli in controlled neocortical networks in vitro. The changes did not occur when the same stimulation was repeated while blocking ionotropic gabaergic and glutamatergic receptors. Even though induction of changes in action potential timing and amplitude depended on synaptic transmission, the expression of these changes persisted in the presence of the synaptic receptor blockers. CONCLUSIONS/SIGNIFICANCE We conclude that, along with changes in synaptic efficacy, propagation plasticity provides a cellular mechanism to tune neuronal network function in vitro and potentially learning and memory in the brain.
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Affiliation(s)
- Douglas J. Bakkum
- Laboratory for Neuroengineering, Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Zenas C. Chao
- Laboratory for Neuroengineering, Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Steve M. Potter
- Laboratory for Neuroengineering, Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail:
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38
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Nave KA, Salzer JL. Axonal regulation of myelination by neuregulin 1. Curr Opin Neurobiol 2006; 16:492-500. [PMID: 16962312 DOI: 10.1016/j.conb.2006.08.008] [Citation(s) in RCA: 344] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 08/25/2006] [Indexed: 01/05/2023]
Abstract
Neuregulins comprise a family of epidermal growth factor-like ligands that interact with ErbB receptor tyrosine kinases to control many aspects of neural development. One of the most dramatic effects of neuregulin-1 is on glial cell differentiation. The membrane-bound neuregulin-1 type III isoform is an axonal ligand for glial ErbB receptors that regulates the early Schwann cell lineage, including the generation of precursors. Recent studies have shown that the amount of neuregulin-1 type III expressed on axons also dictates the glial phenotype, with a threshold level triggering Schwann cell myelination. Remarkably, neuregulin-1 type III also regulates Schwann cell membrane growth to adjust myelin sheath thickness to match axon caliber precisely. Whether this signaling system operates in central nervous system myelination remains an open question of major importance for human demyelinating diseases.
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Affiliation(s)
- Klaus-Armin Nave
- Max Planck Institute of Experimental Medicine, D-37075 Goettingen, Germany.
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39
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Woods IG, Lyons DA, Voas MG, Pogoda HM, Talbot WS. nsf is essential for organization of myelinated axons in zebrafish. Curr Biol 2006; 16:636-48. [PMID: 16581508 DOI: 10.1016/j.cub.2006.02.067] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 02/27/2006] [Accepted: 02/28/2006] [Indexed: 11/16/2022]
Abstract
BACKGROUND Myelinated axons are essential for rapid conduction of action potentials in the vertebrate nervous system. Of particular importance are the nodes of Ranvier, sites of voltage-gated sodium channel clustering that allow action potentials to be propagated along myelinated axons by saltatory conduction. Despite their critical role in the function of myelinated axons, little is known about the mechanisms that organize the nodes of Ranvier. RESULTS Starting with a forward genetic screen in zebrafish, we have identified an essential requirement for nsf (N-ethylmaleimide sensitive factor) in the organization of myelinated axons. Previous work has shown that NSF is essential for membrane fusion in eukaryotes and has a critical role in vesicle fusion at chemical synapses. Zebrafish nsf mutants are paralyzed and have impaired response to light, reflecting disrupted nsf function in synaptic transmission and neural activity. In addition, nsf mutants exhibit defects in Myelin basic protein expression and in localization of sodium channel proteins at nodes of Ranvier. Analysis of chimeric larvae indicates that nsf functions autonomously in neurons, such that sodium channel clusters are evident in wild-type neurons transplanted into the nsf mutant hosts. Through pharmacological analyses, we show that neural activity and function of chemical synapses are not required for sodium channel clustering and myelination in the larval nervous system. CONCLUSIONS Zebrafish nsf mutants provide a novel vertebrate system to investigate Nsf function in vivo. Our results reveal a previously unknown role for nsf, independent of its function in synaptic vesicle fusion, in the formation of the nodes of Ranvier in the vertebrate nervous system.
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Affiliation(s)
- Ian G Woods
- Department of Developmental Biology, Stanford University, California 94305, USA
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40
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Chen S, Velardez MO, Warot X, Yu ZX, Miller SJ, Cros D, Corfas G. Neuregulin 1-erbB signaling is necessary for normal myelination and sensory function. J Neurosci 2006; 26:3079-86. [PMID: 16554459 PMCID: PMC6674097 DOI: 10.1523/jneurosci.3785-05.2006] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To investigate the role of erbB signaling in the interactions between peripheral axons and myelinating Schwann cells, we generated transgenic mice expressing a dominant-negative erbB receptor in these glial cells. Mutant mice have delayed onset of myelination, thinner myelin, shorter internodal length, and smaller axonal caliber in adulthood. Consistent with the morphological defects, transgenic mice also have slower nerve conduction velocity and defects in their responses to mechanical stimulation. Molecular analysis indicates that erbB signaling may contribute to myelin formation by regulating transcription of myelin genes. Analysis of sciatic nerves showed a reduction in the levels of expression of myelin genes in mutant mice. In vitro assays revealed that neuregulin-1 (NRG1) induces expression of myelin protein zero (P0). Furthermore, we found that the effects of NRG1 on P0 expression depend on the NRG1 isoform used. When NRG1 is presented to Schwann cells in the context of cell-cell contact, type III but not type I NRG1 regulates P0 gene expression. These results suggest that disruption of the NRG1-erbB signaling pathway could contribute to the pathogenesis of peripheral neuropathies with hypomyelination and neuropathic pain.
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41
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Abstract
Dys- and demyelination are the common endpoints of several inherited diseases of glial cells, which elaborate myelin and which maintain the myelin sheath very much like an "external" cellular organelle. Whereas some of the genes that are affected by mutations appear to be glial-specific, other genes are expressed in many cell types but their defect is restricted to oligodendrocytes or Schwann cells. Many of the disease genes and their encoded proteins have been studied with the help of mouse models, and a number of different molecular pathomechanisms have emerged which have been summarized in Figure 8. Some of the new concepts in the field, which have been addressed in this review, have only emerged because similar pathomechanisms were discovered for different myelin proteins. Mouse models have clearly helped to address both, the molecular pathology of myelin diseases and the normal function of myelin genes, but as discussed in this review, these questions turned out to be very different. Despite the progress in understanding the role of the abundant myelin proteins, there also remain a number of open questions that concern, among other things, the initial axon-glia recognition, the assembly process of the myelin sheath, and the long-term interaction of axons with their myelinating glia. Finally, animal models of human neurological diseases should not be restricted to the study of pathology, but they should also contribute to the development of experimental treatments. It is encouraging that a few attempts have been made.
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Affiliation(s)
- H Werner
- Zentrum für Molekulare Biologie (ZMBH), Universität Heidelberg, Germany
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42
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Lyons DM, Yang C, Eliez S, Reiss AL, Schatzberg AF. Cognitive correlates of white matter growth and stress hormones in female squirrel monkey adults. J Neurosci 2004; 24:3655-62. [PMID: 15071114 PMCID: PMC6729742 DOI: 10.1523/jneurosci.0324-04.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurobiological studies of stress and cognitive aging seldom consider white matter despite indications that complex brain processes depend on networks and white matter interconnections. Frontal and temporal lobe white matter volumes increase throughout midlife adulthood in humans, and this aspect of aging is thought to enhance distributed brain functions. Here, we examine spatial learning and memory, neuroendocrine responses to psychological stress, and regional volumes of gray and white matter determined by magnetic resonance imaging in 31 female squirrel monkeys between the ages of 5 and 17 years. This period of lifespan development corresponds to the years 18-60 in humans. Older adults responded to stress with greater increases in plasma levels of adrenocorticotropic hormone and modest reductions in glucocorticoid feedback sensitivity relative to young adults. Learning and memory did not differ with age during the initial cognitive test sessions, but older adults more often failed to inhibit the initial learned response after subsequent spatial reversals. Impaired cognitive response inhibition correlated with the expansion of white matter volume statistically controlling for age, stress hormones, gray matter, and CSF volumes. These results indicate that instead of enhancing cognitive control during midlife adulthood, white matter volume expansion contributes to aspects of cognitive decline. Cellular and molecular research combined with brain imaging is needed to determine the basis of white matter growth in adults, elucidate its functions during lifespan development, and provide potential new targets for therapies aimed at maintaining in humans cognitive vitality with aging.
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Affiliation(s)
- David M Lyons
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305-5485, USA.
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43
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Michailov GV, Sereda MW, Brinkmann BG, Fischer TM, Haug B, Birchmeier C, Role L, Lai C, Schwab MH, Nave KA. Axonal neuregulin-1 regulates myelin sheath thickness. Science 2004; 304:700-3. [PMID: 15044753 DOI: 10.1126/science.1095862] [Citation(s) in RCA: 697] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In the nervous system of vertebrates, myelination is essential for rapid and accurate impulse conduction. Myelin thickness depends on axon fiber size. We use mutant and transgenic mouse lines to show that axonal Neuregulin-1 (Nrg1) signals information about axon size to Schwann cells. Reduced Nrg1 expression causes hypomyelination and reduced nerve conduction velocity. Neuronal overexpression of Nrg1 induces hypermyelination and demonstrates that Nrg1 type III is the responsible isoform. We suggest a model by which myelin-forming Schwann cells integrate axonal Nrg1 signals as a biochemical measure of axon size.
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MESH Headings
- Animals
- Axons/physiology
- Axons/ultrastructure
- ErbB Receptors/analysis
- ErbB Receptors/physiology
- Ganglia, Spinal/chemistry
- Gene Targeting
- Genes, erbB
- Genes, erbB-2
- Heterozygote
- Mice
- Mice, Knockout
- Mice, Transgenic
- Models, Neurological
- Myelin Sheath/physiology
- Myelin Sheath/ultrastructure
- Neural Conduction
- Neuregulin-1/genetics
- Neuregulin-1/physiology
- Protein Isoforms/physiology
- Receptor, ErbB-2/analysis
- Receptor, ErbB-2/physiology
- Receptor, ErbB-3/analysis
- Receptor, ErbB-3/physiology
- Schwann Cells/physiology
- Sciatic Nerve/chemistry
- Signal Transduction
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Affiliation(s)
- Galin V Michailov
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
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44
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Abstract
The entire length of myelinated axons is organized into a series of polarized domains that center around nodes of Ranvier. These domains, which are crucial for normal saltatory conduction, consist of distinct multiprotein complexes of cell adhesion molecules, ion channels, and scaffolding molecules; they also differ in their diameter, organelle content, and rates of axonal transport. Juxtacrine signals from myelinating glia direct their sequential assembly. The composition, mechanisms of assembly, and function of these molecular domains will be reviewed. I also discuss similarities of this domain organization to that of polarized epithelia and present emerging evidence that disorders of domain organization and function contribute to the axonopathies of myelin and other neurologic disorders.
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Affiliation(s)
- James L Salzer
- Department of Cell Biology and Neurology, Program in Molecular Neurobiology, Skirball Institute of Biomedical Research, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.
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45
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Gollan L, Sabanay H, Poliak S, Berglund EO, Ranscht B, Peles E. Retention of a cell adhesion complex at the paranodal junction requires the cytoplasmic region of Caspr. J Cell Biol 2002; 157:1247-56. [PMID: 12082082 PMCID: PMC2173544 DOI: 10.1083/jcb.200203050] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
An axonal complex of cell adhesion molecules consisting of Caspr and contactin has been found to be essential for the generation of the paranodal axo-glial junctions flanking the nodes of Ranvier. Here we report that although the extracellular region of Caspr was sufficient for directing it to the paranodes in transgenic mice, retention of the Caspr-contactin complex at the junction depended on the presence of an intact cytoplasmic domain of Caspr. Using immunoelectron microscopy, we found that a Caspr mutant lacking its intracellular domain was often found within the axon instead of the junctional axolemma. We further show that a short sequence in the cytoplasmic domain of Caspr mediated its binding to the cytoskeleton-associated protein 4.1B. Clustering of contactin on the cell surface induced coclustering of Caspr and immobilized protein 4.1B at the plasma membrane. Furthermore, deletion of the protein 4.1B binding site accelerated the internalization of a Caspr-contactin chimera from the cell surface. These results suggest that Caspr serves as a "transmembrane scaffold" that stabilizes the Caspr/contactin adhesion complex at the paranodal junction by connecting it to cytoskeletal components within the axon.
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Affiliation(s)
- Leora Gollan
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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46
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Kretzschmar D, Pflugfelder GO. Glia in development, function, and neurodegeneration of the adult insect brain. Brain Res Bull 2002; 57:121-31. [PMID: 11827744 DOI: 10.1016/s0361-9230(01)00643-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Glial cells have long been viewed as a passive framework for neurons but in the meanwhile were shown to play a much more active role in brain function and development. Several reviews have described the function of glia in the insect embryo. The focus of this review is the role of glial cells in the development and function of the normal and diseased adult brain. In different insect species, a considerable variety of central nervous system glia has been described indicating adaptation to different functional requirements. In the development of the adult visual and olfactory system, glial cells guide incoming axons acting as intermediate targets. Glia are part of the insect blood-brain barrier, provide nourishment for neurons, and help to regulate the extracellular concentration of ions and neurotransmitters. To fulfill these tasks insect glial cells, like vertebrate glia, interact with each other and with neurons, thus influencing neural activity. The examples presented suggest that crosstalk between all brain cells is necessary not only to develop and maintain the complex insect brain but also to endow it with the capacity to respond and adapt to the changing environment.
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Affiliation(s)
- D Kretzschmar
- Institut für Genetik und Neurobiologie, Biozentrum, Universität Würzburg, Würzburg, Germany.
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47
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Baumann N, Pham-Dinh D. Biology of oligodendrocyte and myelin in the mammalian central nervous system. Physiol Rev 2001; 81:871-927. [PMID: 11274346 DOI: 10.1152/physrev.2001.81.2.871] [Citation(s) in RCA: 1203] [Impact Index Per Article: 52.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Oligodendrocytes, the myelin-forming cells of the central nervous system (CNS), and astrocytes constitute macroglia. This review deals with the recent progress related to the origin and differentiation of the oligodendrocytes, their relationships to other neural cells, and functional neuroglial interactions under physiological conditions and in demyelinating diseases. One of the problems in studies of the CNS is to find components, i.e., markers, for the identification of the different cells, in intact tissues or cultures. In recent years, specific biochemical, immunological, and molecular markers have been identified. Many components specific to differentiating oligodendrocytes and to myelin are now available to aid their study. Transgenic mice and spontaneous mutants have led to a better understanding of the targets of specific dys- or demyelinating diseases. The best examples are the studies concerning the effects of the mutations affecting the most abundant protein in the central nervous myelin, the proteolipid protein, which lead to dysmyelinating diseases in animals and human (jimpy mutation and Pelizaeus-Merzbacher disease or spastic paraplegia, respectively). Oligodendrocytes, as astrocytes, are able to respond to changes in the cellular and extracellular environment, possibly in relation to a glial network. There is also a remarkable plasticity of the oligodendrocyte lineage, even in the adult with a certain potentiality for myelin repair after experimental demyelination or human diseases.
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Affiliation(s)
- N Baumann
- Institut National de la Santé et de la Recherche Médicale U. 495, Biology of Neuron-Glia Interactions, Salpêtrière Hospital, Paris, France.
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Sperber BR, McMorris FA. Fyn tyrosine kinase regulates oligodendroglial cell development but is not required for morphological differentiation of oligodendrocytes. J Neurosci Res 2001; 63:303-12. [PMID: 11170180 DOI: 10.1002/1097-4547(20010215)63:4<303::aid-jnr1024>3.0.co;2-a] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The non-receptor protein tyrosine kinase Fyn, which is a member of the Src family of kinases, has been shown to be essential for normal myelination and has been suggested to play a role in oligodendrocyte development. However, oligodendrocyte development has not been studied directly in cells lacking Fyn. Additionally, because Fyn is expressed in neurons as well as oligodendrocytes, it is possible that normal myelination requires Fyn expression in neurons but not in oligodendrocytes. To address these issues, we analyzed the development of oligodendrocytes in neuron-free glial cell cultures from fyn(-/-) mice that express no Fyn protein. We observed that oligodendrocytes develop to the stage where they elaborate an extensive network of membranous processes and express the antigenic components of mature oligodendrocytes in the complete absence of Fyn. However, as compared with fyn(+/+) controls, fewer oligodendroglia developed in fyn(-/-) cell cultures, and a smaller proportion of them matured to the stage characterized by a high degree of morphological complexity. In addition, we found that insulin-like growth factor-I, a potent stimulator of oligodendrocyte development, failed to stimulate morphological maturation of fyn(-/-) oligodendroglia. The pyrazolopyrimidine PP2, believed to be a selective inhibitor of Fyn, did not prevent the development of morphologically complex oligodendrocytes. Unexpectedly, however, it was toxic to both fyn(+/+) and fyn(-/-) glial cells, indicating that this class of inhibitors can have significant effects that are independent of Fyn.
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Affiliation(s)
- B R Sperber
- The Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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Poliak S, Gollan L, Martinez R, Custer A, Einheber S, Salzer JL, Trimmer JS, Shrager P, Peles E. Caspr2, a new member of the neurexin superfamily, is localized at the juxtaparanodes of myelinated axons and associates with K+ channels. Neuron 1999; 24:1037-47. [PMID: 10624965 DOI: 10.1016/s0896-6273(00)81049-1] [Citation(s) in RCA: 372] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Rapid conduction in myelinated axons depends on the generation of specialized subcellular domains to which different sets of ion channels are localized. Here, we describe the identification of Caspr2, a mammalian homolog of Drosophila Neurexin IV (Nrx-IV), and show that this neurexin-like protein and the closely related molecule Caspr/Paranodin demarcate distinct subdomains in myelinated axons. While contactin-associated protein (Caspr) is present at the paranodal junctions, Caspr2 is precisely colocalized with Shaker-like K+ channels in the juxtaparanodal region. We further show that Caspr2 specifically associates with Kv1.1, Kv1.2, and their Kvbeta2 subunit. This association involves the C-terminal sequence of Caspr2, which contains a putative PDZ binding site. These results suggest a role for Caspr family members in the local differentiation of the axon into distinct functional subdomains.
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Affiliation(s)
- S Poliak
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot, Israel
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Osterhout DJ, Wolven A, Wolf RM, Resh MD, Chao MV. Morphological differentiation of oligodendrocytes requires activation of Fyn tyrosine kinase. J Biophys Biochem Cytol 1999; 145:1209-18. [PMID: 10366594 PMCID: PMC2133143 DOI: 10.1083/jcb.145.6.1209] [Citation(s) in RCA: 191] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In the central nervous system, myelination of axons occurs when oligodendrocyte progenitors undergo terminal differentiation and initiate process formation and axonal ensheathment. Although it is hypothesized that neuron-oligodendrocyte contact initiates this process, the molecular signals are not known. Here we find that Fyn tyrosine kinase activity is upregulated very early during oligodendrocyte progenitor cell differentiation. Concomitant with this increase is the appearance of several tyrosine phosphorylated proteins present only in differentiated cells. The increased tyrosine kinase activity is specific to Fyn, as other Src family members are not active in oligodendrocytes. To investigate the function of Fyn activation on differentiation, we used Src family tyrosine kinase inhibitors, PP1 and PP2, in cultures of differentiating oligodendrocyte progenitors. Treatment of progenitors with these compounds prevented activation of Fyn and reduced process extension and myelin membrane formation. This inhibition was reversible and not observed with related inactive analogues. A similar effect was observed when a dominant negative Fyn was introduced in progenitor cells. These findings strongly suggest that activation of Fyn is an essential signaling component for the morphological differentiation of oligodendrocytes.
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Affiliation(s)
- D J Osterhout
- Molecular Neurobiology Program, Skirball Institute, New York University Medical Center, New York 10016, USA
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